In recent years, metal-air batteries have been proposed as next-generation batteries that provide higher energy density than conventional lithium-ion batteries. A metal-air battery is a battery that uses metal as an anode active material and oxygen in the air as a cathode active material. It is said that a metal-air battery theoretically yields more energy per unit weight when metallic lithium is used as its anode active material, and such a configuration is particularly a focus of attention. Such an air-metal battery using metallic lithium as an anode active material is called a lithium-air battery.
Lithium-air batteries are roughly grouped into two types: ones using an aqueous electrolyte inside and ones using a non-aqueous electrolyte inside. Lithium-air batteries using an aqueous electrolyte have the advantage of being less susceptible to moisture in the air than the ones using a non-aqueous electrolyte. However, metallic lithium used as an anode active material reacts chemically by coming into contact with oxygen or water and therefore needs to be isolated from the atmosphere or an aqueous solution. For this isolation, a method has been proposed to provide, for example, a solid electrolyte that conducts lithium ions as an isolation layer.
For example, Patent Document 1 discloses a lithium-air battery using an aqueous electrolyte and having an anode composite in which a polymer electrolyte buffer layer is formed on one side of a metallic lithium plate and is then covered with a glass ceramic that conducts lithium ions.